Light scattering EUVL mask

ABSTRACT

A light scattering EUVL mask and a method of forming the same comprises depositing a crystalline silicon layer over an ultra low expansion substrate, depositing a hardmask over the crystalline silicon layer, patterning the hardmask; etching the crystalline silicon layer, removing the hardmask, and depositing a Mo/Si layer over the crystalline silicon layer, wherein etched regions of the crystalline silicon layer comprise uneven surfaces in the etched regions. The method further comprises depositing a photoresist mask over the hardmask, creating a pattern in the photoresist mask, and transferring the pattern to the hardmask. The Mo/Si layer comprises uneven surfaces conformal with the sloped surfaces of the crystalline silicon layer, wherein the sloped surfaces of the Mo/Si layer may be configured as roughened, jagged, sloped, or curved surfaces, wherein the uneven surfaces deflect incoming extreme ultraviolet radiation waves to avoid collection by exposure optics and prevent printing onto a semiconductor wafer.

BACKGROUND OF INVENTION

1. Field of the Invention

The invention generally relates to reflective masks, and moreparticularly to a light scattering and radiation reflective EUVL mask.

2. Description of the Related Art

The optical lithographic technique that is used to image wafersthroughout the semiconductor industry relies on transparent masks totransfer an image from the mask to the wafer. As wafer images shrink,new ways of imaging the wafer resist are needed. One likely candidatefor the Next Generation Lithography uses Extreme Ultraviolet (EUV) lightto image. At the 13.4 nm EUV wavelength, materials are too absorptive tobuild a transmissive mask, so reflective ones are used instead.Conventional Extreme Ultraviolet Lithography (EUVL) masks, such as themask illustrated in FIG. 1, are built by depositing a reflective filmonto an ultra low expansion (ULE) substrate 10. Material properties ofULE substrates are well known in the art. This film can be composed ofmany different materials. The most commonly deployed reflective Braggmirror for EUVL mask applications is created with multiple (as many asforty or more) alternating bilayers of molybdenum (Mo) and silicon (Si),finishing with a protective Si cap shown collectively as a Mo/Simultilayer 20. A buffer layer 30 and absorber layer 40 are thendeposited on the multilayer stack 20. Additional layers can be depositedanywhere within the capping/buffer/absorber stack for differentpurposes, such as to provide an etch stop or conductiveinspection/repair layer. The mask pattern is written onto a resist layerusing standard mask patterning processes. A dry etch transfers thepattern through the absorber layer. Inspection and repair are performedto ensure that the absorber pattern matches the design data and then thefinal pattern is transferred through the buffer layer to expose thereflective multilayer surface.

There are many material challenges inherent in building and using anEUVL mask. One fundamental mask issue is the selection of absorber andbuffer materials that combine ideal chemical durability, adhesion, dryetch characteristics and optical. Moreover, maintaining the quality (andhence reflectivity) of the capping layer's reflective surface duringmask processing is difficult.

Generally, conventional optical masks include transmissive regions thatpermit light to pass onto the wafer and absorptive regions that blockthe light. However, the masks used in the EUVL system, introduce a newset of challenges. Because an EUVL mask is reflective, the EUV radiationmust be exposed to the mask surface at an angle such that the patternwill reflect onto the surface of the wafer. Specifically, light incidenton the exposed reflective surface is reflected. Light incident on thepatterned absorber film is absorbed, not reflected; an essentialcomponent to imaging. A by-product of this absorption is that theradiation heats the mask and must be controlled to avoid patterndistortion and also to limit heat-induced wear that would decrease masklifetime. Experiments have shown that 5 degrees is the optimal angle ofexposure.

The absorber stack height is finite and creates a shadow under the angleof illumination which blurs the edge of the raised absorber when imaged.This reduction in contrast is a function of the angle of the incidentexposure light and both the absorber and buffer layer thickness. Reducedcontrast at the pattern edges is a significant issue since it can resultin shifted or mis-sized images on the wafer.

The industry has sought to overcome these identified challenges, yet asolution has not been adequately defined. Therefore, due to thelimitations of the conventional devices and processes, there is a needfor a novel EUVL mask which overcomes the problems associated with thestandard techniques.

SUMMARY OF INVENTION

The invention overcomes the above-identified problems by eliminatingboth the buffer and absorber layers of the mask stack entirely. Theinvention provides a light scattering extreme ultraviolet lithographymask wherein a silicon molybdenum multilayer is deposited over apatterned blank with specific topography that causes the EUV radiationto be reflected in areas where the exposure light is intended to impingeon the wafer and scattered in areas where the light is not intended toreach the wafer. The topography in the regions intended to reflect lightonto the wafers are configured as flat regions. However, in regionswhere the EUV radiation is not intended to reach the surface of thewafer, the topography is configured such that it scatters the radiationout of the imaging optics of the stepper and hence would not print.

Specifically, the invention provides an extreme ultraviolet lithographymask comprising an ultraviolet reflective region and an ultravioletscattering region, wherein the reflective region and the scatteringregion are comprised of the same material. The reflective regioncomprises a molybdenum and silicon multilayer, wherein the multilayercomprises a flat surface configured to reflect incoming ultravioletradiation waves for imaging on a semiconductor wafer. The scatteringregion comprises a molybdenum and silicon multilayer, wherein themultilayer comprises one or more sloped surfaces configured at an anglechosen to deflect incoming ultraviolet radiation waves to prevent/avoidcollection by the exposure optics and to prevent imaging onto asemiconductor wafer, wherein the angle is greater than a collectionangle of the exposure optics. In alternate embodiments, the scatteringregion comprises a roughened surface, a jagged surface, or a curvedsurface configured to deflect incoming ultraviolet radiation waves toprevent/avoid collection by the exposure optics and to prevent printingonto a semiconductor wafer.

Moreover, the invention provides a light scattering reflective maskcomprising an ultra low expansion substrate, a crystalline silicon layeron top of the ultra low expansion substrate, and a radiation reflectingand light scattering multilayer comprising molybdenum and silicon on topof the crystalline silicon layer. The multilayer conforms to theunderlying silicon layer to have a level portion and an uneven portion.The level portion is configured to reflect incoming ultravioletradiation waves onto a semiconductor wafer. In one embodiment, theuneven portion comprises a sloped configuration arranged at an angle todeflect incoming ultraviolet radiation waves to prevent light fromreaching the semiconductor wafer. In another embodiment, the unevenportion comprises a roughened surface configured to deflect incomingultraviolet radiation waves to prevent/avoid collection by the exposureoptics and to prevent printing onto a semiconductor wafer. In yetanother embodiment, the uneven portion comprises a jagged surfaceconfigured to deflect incoming ultraviolet radiation waves toprevent/avoid collection by the exposure optics and to prevent printingonto a semiconductor wafer. Alternatively, the uneven portion comprisesa curved surface configured to deflect incoming ultraviolet radiationwaves to prevent/avoid collection by the exposure optics and to preventprinting onto a semiconductor wafer.

Another aspect of the invention provides a method of forming an extremeultraviolet lithography mask by anodically bonding a crystalline siliconlayer on top of an ultra low expansion substrate, and then depositing aconformal multilayer comprising molybdenum and silicon on top of thecrystalline silicon layer, wherein the multilayer comprises a surfacehaving a level portion to reflect light onto the wafer and an unevenportion to scatter light so that it does not impinge on the wafer. Priorto the step of depositing the reflective multilayer, the method furthercomprises depositing a hardmask over the crystalline silicon layer,depositing a photoresist mask over the hardmask, creating a pattern inthe photoresist mask, and transferring the pattern to the hardmask. Themethod further comprises etching the crystalline silicon layer toproduce an uneven surface in etched regions of the crystalline siliconlayer, and removing the hardmask. Additionally, the pattern istransferred to the hardmask using a plasma etch, wherein the etching ofthe crystalline silicon comprises an anisotropic wet etch, which isperformed using an alkaline solution such as aqueous potassium hydroxide(KOH), tetramethylammonium hydroxide (TMAH), or ethylene diaminepyrocatechol (EDP). Furthermore, the etching is performed along <100>lattice planes of the crystalline silicon layer.

Moreover, the level regions are configured to reflect incomingultraviolet radiation waves for printing a semiconductor wafer, and in afirst embodiment, the uneven regions comprises sloped surfaces conformalto the underlying crystalline silicon layer, wherein the sloped surfacesare configured at an angle to deflect incoming extreme ultravioletradiation waves to prevent printing to a semiconductor wafer, whereinthe angle is 54 degrees from normal. In a second embodiment, the methodcomprises configuring the uneven portion to have a roughened surface todeflect incoming ultraviolet radiation waves to prevent printing to asemiconductor wafer. In a third embodiment, the method comprisesconfiguring the uneven regions to have a jagged surface to deflectincoming ultraviolet radiation waves to prevent printing to asemiconductor wafer. In another embodiment, the method comprisesconfiguring the uneven regions to have a curved surface to deflectincoming ultraviolet radiation waves to prevent printing to asemiconductor wafer.

The invention eliminates the need for a buffer or absorber layer withinthe mask stack and overcomes the problems inherent with conventionalEUVL masks previously described. Because the multilayer is deposited asthe final step in the mask fabrication, the multilayer will not besubjected to the plasma etches, wet etches, and multiple cleans thatdegrade the multilayer in the standard EUVL mask process andconsequently reduce the mask reflectivity. In this invention, the higherreflectivity increases the mask contrast between reflective andscattering regions, decreases the required exposure time, and reducesthe amount of radiation that is absorbed by the mask.

The inventive mask comprises a substrate (which may include a bondedcrystalline Si layer) and the multilayer without an absorber or bufferlayer. The absence of a raised absorber stack eliminates the shadoweffect during wafer printing. This results in an abrupt transition fromdark to reflective mask regions and the effect is an improvement in theedge contrast on the lithographic wafer.

These and other aspects of the invention will be better appreciated andunderstood when considered in conjunction with the following descriptionand the accompanying drawings. It should be understood, however, thatthe following description, while indicating preferred embodiments of theinvention and numerous specific details thereof, is given by way ofillustration and not of limitation. Many changes and modifications maybe made within the scope of the invention without departing from thespirit thereof, and the invention includes all such modifications.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be better understood from the following detaileddescription with reference to the drawings, in which:

FIG. 1 is a schematic cross-sectional diagram of a conventional EUVLmask;

FIG. 2 is a schematic cross-sectional diagram of an EUVL mask accordingto an embodiment of the invention;

FIG. 3( a) through 3(e) are schematic cross-sectional diagramsillustrating sequential processing steps in the manufacturing of an EUVLmask according to an embodiment of the invention;

FIG. 4 is a schematic cross-section diagram of a EUVL mask according toan alternate embodiment of the invention; and

FIGS. 5( a) and 5(b) are flow diagrams illustrating preferred methods ofthe invention.

DETAILED DESCRIPTION

The invention and the various features and advantageous details thereofare explained more fully with reference to the non-limiting embodimentsthat are illustrated in the accompanying drawings and detailed in thefollowing description. It should be noted that the features illustratedin the drawings are not necessarily drawn to scale. Descriptions ofwell-known components and processing techniques are omitted so as to notunnecessarily obscure the invention. The examples used herein areintended merely to facilitate an understanding of ways in which theinvention may be practiced and to further enable those of skill in theart to practice the invention. Accordingly, the examples should not beconstrued as limiting the scope of the invention.

As previously mentioned, there is a need for a novel EUVL mask andmethod of manufacturing an EUVL mask, which overcomes the problemsassociated with the standard masks and associated manufacturingtechniques. Referring now to the drawings, and more particularly toFIGS. 2 through 5( b), there are shown preferred embodiments of theinvention.

In a first embodiment, the invention provides an EUVL mask that haspartially sloped surfaces configured as sloped sidewalls as depicted inFIG. 2. While not explicitly shown in the figures, those skilled in theart would readily understand that the sloped sidewalls could beconfigured to be generally curvilinear (either convexly or concavely)shaped. As illustrated in FIG. 2, the incoming EUV radiation at 5degrees is depicted as the solid arrows, and normal EUV reflection isshown as the dashed arrows. The radiation that is reflected off of theflat surface of the multilayer 160, shown with the dashed arrows, willbe printed on the wafer. In the patterned areas with the slopedsidewalls, the radiation is deflected at an angle that will not print onthe wafer. The out of plane reflections are depicted as the dottedarrows in FIG. 2.

The invention configures a ULE substrate 100 with a layer of crystallinesilicon 110.

FIGS. 3( a) through 3(e) illustrate the sequential processing stepsinvolved in manufacturing an EUVL mask according to the invention.Preferably, the invention joins a layer of crystalline silicon 110 on aquartz substrate 100 by anodically bonding a silicon wafer to quartz asshown in FIG. 3( a). Anodic bonding is a process well-known to thoseskilled in the art, and may include the general process described inU.S. Pat. No. 6,368,942, the complete disclosure of which, in itsentirety, is herein incorporated by reference.

The next steps of the invention involve depositing a hardmask 120 andresist 130 upon the crystalline silicon layer 110 as shown in FIG. 3(b). Then, as illustrated in FIG. 3( c), the desired pattern is writtenin the resist 130 and the pattern is transferred to the hardmask 120through a plasma etch. This creates opened regions (openings) 140 in thehardmask 120, wherein the openings 140 are patterned down to the surface115 of the underlying crystalline silicon 110.

The next step, as shown in FIG. 3( d), is to wet etch the crystallinesilicon 110 anisotropically, preferably with a wet etch solution, suchas aqueous potassium hydroxide (KOH), tetramethylammonium hydroxide(TMAH), or ethylene diamine pyrocatechol (EDP). The silicon 110 isetched along the <100> lattice planes preferably giving approximately a54 degree sidewall slope of crystalline silicon 110 in the openedregions 140 (thereby resulting in opened sloped regions 155) defined bythe crystalline silicon 110, thereby resulting in sloped sidewalls 150.The <111> crystal plane of crystalline silicon etches much more slowlythat the other crystal planes of silicon in alkaline solutions by atleast a factor of 100 (more slowly). Hence, in <100> silicon, slopedsidewalls 150 with an angle of 54 degrees result because the <111> planedoes not etch as fast as the other crystal planes. Ultimately, if thefeatures are small enough or the silicon thick enough, the reaction isself-terminating. For instances where there are large regions of openspace which are required to absorb or scatter the incident EUVL light,this pattern can be repeated. This creates multiple “wells” that acttogether to reflect the EUV light out of the focal plane.

After the hardmask 120 is stripped, a Mo/Si multilayer 160 is depositedover the crystalline silicon layer 110 and is filled into the openedsloped region 155 of the crystalline silicon layer 110. As shown in FIG.3( e) the Mo/Si multilayer 160 assumes the configuration of theunderlying etched crystalline silicon layer 110 and includes slopedregions 165 having sloped sidewalls 180 configured above the underlyingsloped region 155 of the crystalline silicon layer 110. Accordingly, theMo/Si multilayer 160 completely fills the sloped region 155 thecrystalline silicon layer 110. Furthermore, the Mo/Si layer 160 furthercomprises selective flat (level) surfaces 170 configured in between theuneven surfaces (uneven regions) 165.

Additionally, as shown in FIG. 3( e), the sloped sidewalls 180 areconfigured at an angle θ which will allow deflection of incomingultraviolet radiation waves in order to prevent collection by exposureoptics and to prevent printing onto a semiconductor wafer, wherein theangle θ is greater than a collection angle of the exposure optics. Inone embodiment, the angle is created by etching the crystalline siliconlayer 110 at an angle of θ that is 54 degrees from normal. Thereflective multilayer is conformal to the underlying crystalline silicon110 and matches the 54 degree. FIG. 4 illustrates an alternateembodiment of the invention, wherein the uneven portion 190 of the Mo/Simultilayer 160 is formed by roughening the surface 170 of the Mo/Simultilayer 160. Techniques that include reactive ion etching or wetetching can be used to roughen the surface 170. As shown in themagnified view within the dashed oval circle in FIG. 4, the unevenportion 190 may be configured as a jagged surface. The jagged surfacecan be defined as any roughness that deviates significantly from thetarget specification of <0.15 nm RMS (root mean square) surfaceroughness. A roughness of approximately 10 nm would prevent effectivereflection of incident EUV radiation. The roughness is analogous to amicro version of the sloped surface that can be created with theanisotropic wet etching of silicon described above, and serves the samepurpose on a smaller scale.

In FIGS. 5( a) and 5(b) flow diagrams illustrating preferred methods offorming an EUVL mask according to the invention are described.Generally, as provided in FIG. 5( a), a method of forming an EUVL maskcomprises forming 200 a radiation reflective region 170 on a surface ofthe mask, and forming 210 a light scattering region 165, 190 on thesurface of the mask, wherein the radiation reflective region 170 and thelight scattering region 165, 190 are comprised of the same material(Mo/Si) 160.

More specifically, as shown in FIG. 5( b), the method of forming an EUVLmask according to the first embodiment of the invention comprisesdepositing 300 a crystalline silicon layer 110 over an ULE substrate100, depositing 210 a hardmask 120 over the crystalline silicon layer110, depositing 320 a photoresist mask 130 over the hardmask 120,creating 330 a pattern in the photoresist mask 130, transferring 340 thepattern to the hardmask 120, etching 350 the crystalline silicon layer110 to produce sloped sidewalls 180 in etched regions 165 of thecrystalline silicon layer 110, removing 360 the hardmask 120, anddepositing 370 a Mo/Si layer 160 over the crystalline silicon layer 110.The Mo/Si layer 160 further comprises flat surfaces 170 configured toreflect incoming extreme ultraviolet radiation waves for printing asemiconductor wafer. Additionally, the Mo/Si layer 160 further comprisessloped sidewalls 180 corresponding to the sloped sidewalls 150 of thecrystalline silicon layer 110. Furthermore, the sloped sidewalls 180 ofthe Mo/Si layer 160 are configured at an angle of at least 54 degreesfrom normal to deflect incoming extreme ultraviolet radiation waves toprevent printing to a semiconductor wafer.

The invention eliminates the need for a buffer or absorber layer withinthe mask stack and overcomes the problems inherent with conventionalEUVL masks previously described. Because the multilayer is deposited asthe final step in the mask fabrication, the multilayer will not besubjected to the plasma etches, wet etches, and multiple cleans thatdegrade the multilayer and consequently reduce the mask reflectivity.This higher reflectivity increases the mask contrast between reflectiveand scattering regions, decreases the required exposure time, andreduces the amount of radiation that is absorbed by the mask. Stepperthroughput is the number of wafers that can be printed in a given timeperiod, such as wafers/hour. Decreasing exposure time increases asdescribed above directly increases stepper throughput.

Moreover, the inventive mask comprises a substrate 100 (which mayinclude a bonded crystalline Si layer) and a multilayer 160 formedwithout an absorber or buffer layer. The absence of a raised absorberstack eliminates the shadow effect during wafer printing. This resultsin an abrupt transition from dark to reflective mask regions and theeffect is an improvement in the edge contrast on the lithographic wafer.An additional advantage achieved by the invention is that the radiationis reflected so that there is less heating of the EUVL mask, which is asignificant concern for image control and lifetime.

Generally, the invention includes a novel mask including an absorbingregion 110 that is created before the Mo/Si multilayer 160 is deposited.The patterning can be achieved by either roughening the surface of themask in regions 190 where the EUV light is not intended to reach theprinted wafer surface or forming a grid of sloped sidewalls 180 in theregions 165 where the EUV light is not intended to reach the printedwafer surface. Techniques that include reactive ion etching or wetetching techniques can be used to either roughen the surface 190 orcreate the sloped sidewalls 180. The level pattern 170 that is to bereflected to the printed wafers surface will remain smooth and planar.After multilayer deposition 370, the uneven patterned areas 165, 190 actas the absorber of the EUVL mask because the reflective capabilities ofthe Mo/Si film 160 are locally destroyed. However, as described above,these regions 165, 190 do not actually absorb the EUV radiation butrather deflect the EUV radiation at an angle that will not develop thephotoresist on the wafer.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the invention that others can, by applyingcurrent knowledge, readily modify and/or adapt for various applicationssuch specific embodiments without departing from the generic concept,and, therefore, such adaptations and modifications should and areintended to be comprehended within the meaning and range of equivalentsof the disclosed embodiments. It is to be understood that the phrases orterminology employed herein is for the purpose of description and not oflimitation. Therefore, while the invention has been described in termsof preferred embodiments, those skilled in the art will recognize thatthe invention can be practiced with modification within the spirit andscope of the appended claims.

1. An extreme ultraviolet lithography (EUVL) mask comprising an uppersurface, wherein said upper surface consists of a reflective surface,said EUVL mask comprising: an extreme ultraviolet reflective region; andan extreme ultraviolet scattering region, wherein said extremeultraviolet reflective region and said extreme ultraviolet scatteringregion are comprised of a same material.
 2. The mask of claim 1, whereinsaid reflective region comprises a reflective multilayer comprisingmolybdenum and silicon, and wherein said multilayer comprises a flatsurface configured to reflect incoming radiation waves for printing asemiconductor wafer.
 3. The mask of claim 1, wherein said scatteringregion comprises a multilayer comprising molybdenum and silicon, andwherein said multilayer comprises a sloped surface configured at anangle to deflect incoming ultraviolet radiation waves to preventcollection by exposure optics and to prevent printing onto asemiconductor wafer.
 4. The mask of claim 3, wherein said angle isgreater than a collection angle of said exposure optics.
 5. The mask ofclaim 1, wherein said scattering region comprises a roughened surfaceconfigured to deflect incoming ultraviolet radiation waves to preventcollection by exposure optics and to prevent printing onto asemiconductor wafer.
 6. The mask of claim 1, wherein said scatteringregion comprises jagged surfaces configured to deflect incomingultraviolet radiation waves to prevent collection by exposure optics andto prevent printing onto a semiconductor wafer.
 7. The mask of claim 1,wherein said scattering region comprises a curved surface configured todeflect incoming ultraviolet radiation waves to prevent collection byexposure optics and to prevent printing onto a semiconductor wafer.
 8. Aradiation scattering reflective mask comprising an upper surface,wherein said upper surface consists of a reflective surface, saidradiation scattering reflective mask comprising: an ultra low expansionsubstrate; a crystalline silicon layer adjacent to said ultra lowexpansion substrate; and a multilayer comprising molybdenum and siliconadjacent to said crystalline silicon layer, wherein said multilayercomprises a surface having level portions and uneven portions.
 9. Themask of claim 8, wherein said uneven portions comprise slopedconfigurations arranged at an angle to deflect incoming ultravioletradiation waves to prevent collection by exposure optics and to preventprinting onto a semiconductor wafer.
 10. The mask of claim 9, whereinsaid crystalline silicon layer comprises a sloped surface, wherein saidsloped surface of said crystalline silicon layer is aligned with saidsloped configuration of said uneven portion.
 11. The mask of claim 9,wherein said angle is greater than approximately 54 degrees from normal.12. The mask of claim 8, wherein said level portions are configured toreflect incoming ultraviolet radiation waves for printing asemiconductor wafer.
 13. The mask of claim 8, wherein said multilayerlayer reflects radiation.
 14. The mask of claim 8, wherein saidmultilayer scatters light on said uneven portions.
 15. The mask of claim8, wherein said uneven portions comprises a roughened surface configuredto deflect incoming ultraviolet radiation waves to prevent collection byexposure optics and to prevent printing onto a semiconductor wafer. 16.The mask of claim 8, wherein said uneven portions comprise jaggedsurfaces configured to deflect incoming ultraviolet radiation waves toprevent collection by exposure optics and to prevent printing onto asemiconductor wafer.
 17. The mask of claim 8, wherein said unevenportions comprise curved surfaces configured to deflect incomingultraviolet radiation waves to prevent collection by exposure optics andto prevent printing onto a semiconductor wafer.
 18. An extremeultraviolet lithography mask comprising: a substrate; a crystallinesilicon layer over said substrate; and a multilayer comprisingmolybdenum and silicon over said crystalline silicon layer, wherein saidmultilayer comprises a reflective region and a scattering region, andwherein said multilayer comprises an upper surface that consists of areflective surface.
 19. The mask of claim 18, wherein said substratecomprises an ultra low expansion substrate.
 20. The mask of claim 18,wherein said scattering region comprises surfaces having slopedconfigurations arranged at an angle to deflect incoming ultravioletradiation waves to avoid collection by exposure optics and to preventprinting onto a semiconductor wafer.
 21. The mask of claim 20, whereinsaid crystalline silicon layer comprises sloped surfaces, wherein saidsloped surfaces of said crystalline silicon layer are aligned with saidsloped configuration of said surfaces of said scattering region.
 22. Themask of claim 20, wherein said angle is approximately 54 degrees fromnormal.
 23. The mask of claim 18, wherein said reflective region isconfigured to reflect incoming radiation waves for printing asemiconductor wafer.
 24. The mask of claim 18, wherein said scatteringregions comprise roughened surfaces configured to deflect incomingultraviolet radiation waves to avoid collection by exposure optics andto prevent printing onto a semiconductor wafer.
 25. The mask of claim18, wherein said scattering region comprises jagged surfaces configuredto deflect incoming radiation waves to avoid collection by exposureoptics and to prevent printing onto a semiconductor wafer.
 26. The maskof claim 18, wherein said scattering region comprises curved surfacesconfigured to deflect incoming ultraviolet radiation waves to avoidcollection by exposure optics and to prevent printing onto asemiconductor wafer.
 27. A method of forming an extreme ultravioletlithography (EUVL) mask comprising an upper surface, wherein said uppersurface consists of a reflective surface, said method comprising:bonding a crystalline silicon layer adjacent to a substrate; and forminga multilayer comprising molybdenum and silicon adjacent to saidcrystalline silicon layer, wherein said multilayer comprises a surfacehaving level portions and uneven portions.
 28. The method of claim 27,wherein said crystalline silicon layer is anodically bonded to saidsubstrate.
 29. The method of claim 27, wherein prior to said step offorming a multilayer, said method further comprises: depositing a hardmask over said crystalline silicon layer; depositing a photoresist maskover said hardmask; creating a pattern in said photoresist mask; andtransferring said pattern to said hardmask.
 30. The method of claim 29,further comprising: etching said crystalline silicon layer to produceuneven surfaces in etched regions of said crystalline silicon layer; andremoving said hardmask.
 31. The method of claim 29, wherein said patternis transferred to said hardmask using a plasma etch.
 32. The method ofclaim 30, wherein said etching of crystalline silicon layer comprises ananisotropic silicon wet etch.
 33. The method of claim 32, wherein saidwet etch is performed using an alkaline solution.
 34. The method ofclaim 27, wherein said substrate is formed of an ultra low expansionsubstrate.
 35. The method of claim 30, wherein said etching is performedalong <100> lattice planes of said crystalline silicon layer.
 36. Themethod of claim 27, wherein said multilayer reflects radiation andscatters light.
 37. The method of claim 27, wherein said level portionsare configured to reflect incoming ultraviolet radiation waves forprinting onto a semiconductor wafer.
 38. The method of claim 27, whereinsaid uneven portions comprise sloped surfaces conformal to theunderlying crystalline silicon layer, wherein said sloped surfaces areconfigured at an angle to deflect incoming extreme ultraviolet radiationwaves to avoid collection by exposure optics and to prevent printingonto a semiconductor wafer.
 39. The method of claim 38, wherein saidangle is approximately 54 degrees from normal.
 40. The method of claim27, further comprising configuring said uneven portions to have aroughened surface to deflect incoming ultraviolet radiation waves toavoid collection by exposure optics and to prevent printing onto asemiconductor wafer.
 41. The method of claim 27, further comprisingconfiguring said uneven portions to have jagged surfaces to deflectincoming ultraviolet radiation waves to avoid collection by exposureoptics and to prevent printing onto a semiconductor wafer.
 42. Themethod of claim 27, further comprising configuring said uneven portionsto have curved surfaces to deflect incoming radiation waves to avoidcollection by exposure optics and to prevent printing onto asemiconductor wafer.
 43. A method of forming an extreme ultravioletlithography (EUVL) mask comprising an upper surface, wherein said uppersurface consists of a reflective surface, said method comprising:forming reflective regions on surfaces of said mask; and formingscattering regions on said surfaces of said mask, wherein saidreflective regions and said scattering regions comprise a same material.44. The method of claim 43, wherein in said step of forming reflectiveregions, said reflective regions are formed of a multilayer comprisingmolybdenum and silicon, and wherein said multilayer comprises a flatsurface configured to reflect incoming radiation for collection byexposure optics and for printing onto a semiconductor wafer.
 45. Themethod of claim 43, wherein in said step of forming scattering regions,said scattering regions are formed of a multilayer comprising molybdenumand silicon, and wherein said multilayer conforms to sloped surfacesconfigured at an angle to deflect incoming radiation to avoid collectionby exposure optics and to prevent printing onto a semiconductor wafer.46. The method of claim 43, further comprising configuring saidscattering regions to have roughened surfaces to deflect incomingultraviolet radiation waves to avoid collection by exposure optics andto prevent printing onto a semiconductor wafer.
 47. The method of claim43, further comprising configuring said scattering regions to have ajagged surfaces to deflect incoming ultraviolet radiation waves to avoidcollection by exposure optics and to prevent printing onto asemiconductor wafer.
 48. The method of claim 43, further comprisingconfiguring said scattering regions to have curved surfaces to deflectincoming radiation to avoid collection by exposure optics and to preventprinting onto a semiconductor wafer.